The present invention relates to an alternating presser foot with a vertically movable sole portion, fixed in the feeding direction of the feed dog, and provided with a clamping pressure foot which can be placed on the sewing material relative to the movable sole portion by means of a drive lever cooperating with the needle bar and which moves along with the sewing material in the feeding direction of the feed dog.
A presser foot of this type has been known, for example, from Swiss Patent No. 503,824. The drive lever, connected to the needle bar for movement therewith, cooperates by way of a first roller with a cam lever for the purpose of operating the fixed sole portion. A second roller of the drive lever cooperates with a V-shaped cam for the purpose of centering the clamping pressure foot, encompassing the fixed sole portion, in its neutral position. The clamping pressure foot is movably connected to the shank of the presser foot by way of a parallelogram, the roller of the drive lever impinging almost vertically on the cam lever forming part of the parallelogram. This arrangement tends to generate a large amount of noise and is prone to increased wear and tear. The same holds true for the entering of the second roller into the V-shaped cam groove, the position of which is determined by the position of advancement of the entrained sole portion. The angle of impingement of this second roller is variable so that the noise also becomes greater, the longer the advancement.
Another disadvantage of this kind of arrangement is the small fixed sole portion which, although securing the sewing material together with the penetrated needle against shifting in the sewing direction, can prevent only with difficulties, the rotation of the sewing material about the needle penetration point. The small basal surface of the fixed sole portion can furthermore cause markings on sensitive sewing material which thereafter remain visible.
In contrast thereto, the present invention has the object of providing an alternating presser foot of the aforementioned type wherein there is not only the assurance of a perfect centering of the clamping pressure foot in its neutral position, but wherein the presser foot also operates at low noise and with low wear and tear.